Umaima is 4 times as old as Nadia and is also 27 years older than Nadia. How old is Nadia?
Solution: We can use the given information to write down two equations that describe the ages of Umaima and Nadia. Let Umaima's current age be $u$ and Nadia's current age be $n$ $u = 4n$ $u = n + 27$ Now we have two independent equations, and we can solve for our two unknowns. Since we are looking for $n$ , and both of our equations have $u$ alone on one side, this is a convenient time to use elimination. Subtracting the second equation from the first equation, we get: $0 =$ $4n$ $-$ $ (n + 27)$ which combines the information about $n$ from both of our original equations. Solving for $n$ , we get: $3 n = 27$ $n = 9$.